Continuously tunable femtosecond pulses covering 2·1–2·5 μm from an optical parametric oscillator based on RbTiOAsO4

The operation of a synchronously pumped femtosecond optical parametric oscillator based on the nonlinear material RbTiOAsO4 is described. The idler output was continuously tuned from 2·1 to 2·5 μm, the pulses having powers as high as 140 mW and durations as short as 140 fs. Characterization of the pulses was achieved by use of a novel autocorrelator based on an InGaAs photodiode and a LiNbO3 frequency-doubling crystal, capable of producing high quality interferometric and intensity autocorrelations.